Process of cracking oil



Sept- 10, 41929. E. w. lsoM Er AL 1,727,707

PROCESS OF CRACKING OIL Filed Nov. 17. 1924 /V/JE/VSER, F565/ VER Q im (\I a0-MMM .fmc. my.)

Patented Sept. 1o, 1929.

4UNITED STATES PATENT OFFICE.

EDWARD W. ISOM', OIF` LOCUST VALLEY, NEW YORK, AND EUGENE C. HERTHEL AND HARRY L, PELZER, 0F `GHICAGO, ILLINOIS, ASSIGNORS TO SIN CLAIR BEFINING COMPANY, 0F CHICAGO, ILLINOIS, CORPORATION 0F MAINE.

PROCESS 0F CRACKING OIL.

Application iled Novemberr 17, 1924. Serial No. 750,240.

In the processes commonly employed for cracking hydrocarbons, the material is heated to a cracking temperature under pressure, the vapors of the cracked hydrocarbons being driven off and condensed. In the continuous process lwhich is generally favored, fresh material to be cracked is fed into the still during the major portion of the run and during a considerable period thereof tar is drawn off in order to prevent the accumulation of too large a proportion of heavy material. In what is known as the semi-continuous process, fresh oil is fed in during the run, but no tar is drawn oil'. In both of these methods of operating, the process is carried on only to a point at which the residue in the still remains in a sufficiently fluid condition to be largely drawn off from the still in the liquid state. It has been proposed to carry the process on to the production of dry coke from the residue in the still, but little practical success has been had in the eifort'to carry this proposal into effect.

Our invention relates to a semi-continuous process in which the residue in the still is reduced to a dry dense coke which can be readily removed from the still at the end of the operation and is suitable for use as domestic fuel and for other purposes for which coke from coke stills is commonly employed. Among the advantages of our improved process is the production of a valuable coke, fuel economy due to the fact that a smaller total amount of oil is heated for a given production of distillate, an increase in the amount of distillate produced from the material treated, an increase in the rate of distillate and gasoline production and an elimination of. certain objectionable features of the continuous process which have been experienced in connection with the removal of tar, such as the plugging of the tar lines and coolers. As cofnpared to the semi-continuous operation in which the residuum is reduced only to pitch we have the advantage of the absence of plugged tar lines and coolers from the pumping of batch bottoms and the avoidance of the diliculties and objections incident to the handling of pitch, among which may be mentioned the difficulty and delay in cooling. due

zation of the pitch constituents and also introduce a substance in a gaseous or vapor state which reduces the partial pressure of the pitch and therefore facilitates its vaporization. The components of the pitch are driven olf in the order of their gravities as the pressure is lowered so that when it is down to 40 pounds all of the heat is available for vaporizing the heaviest components.

`Preferably, the introduced substance is preheated to a temperature above the normal cracking temperature employed in the still so that additional heat is supplied to maintain a temperature suicient to both vaporize and decompose the pitch constituents. In our 'improved'process, the introduced substance in question is so supplied as to permeate the entire charge in the shell and preferably it is introduced at the bottom thereof so that in. passing upwardly through the coke it serves as a carrier to assist in the removal of the heavier vapors. Other features and advantages of our process will be understood from the more specific disclosure thereof in connection with the drawing accompanying and forming a part of this specification.

The drawing is diagrammatic and represents a suitable apparatus for carrying out our process partly in elevation and partly in section.

Referring now to the drawing, 1 is a shell into which is charged the oil to be treated. We have found it satisfactory not to directly heat the shell, though it may be gently heated without. departing from our invention. We have shown no direct heating means however. The oil is heated by a heating medium .injected into the body thereof as will presently be described. Manholes 2 2 are provided for the removal of coke at the end of the operation or run and an emergency draw-off 3 is provided in case for any reason it may be necessary to remove the residuum in the liquid condition. The vapors from the still are carried through a line 4 to a reflux condenser or heat interchanger 5 in Which the vapors of the heavier hydrocarbons are condensed. The disposal of the condensate will be presently described. From the condenser 5, the lighter vapors and gas are conducted by a line 6 to a second heat interchanger 7 in Which a further condensation of vapors takes place and from Which the lighter vapors including the'desired distillatev and incondensa'ble gases are led by pipe 8 to a condenser and receiver. The latter may be of the Well-known types employed in connection with cracking stills and provided with the necessary valves for pressure control. After the proper charge has been introduced into the shell 1 in heated condition in the manner hereinafter described it ismaintained at a cracking temperature by the injection thereinto of lighter hydrocarbons in 'the form of gas or vapor. For this purpose,

relatively light oil, which may be gas oil, is fed from a suitable source 9 through a superheater 10 in which it is vaporized-before being injected into the still 1. From the supply 9, the lighter oil passes through a pipe 11, meter 12 and valve`13 to a pump 14 by which it is forced through pipe 15 into the heating coil 16. The heating coil is maintained at a temperature considerably above the cracking point so that the oil fed therethrough is vaporized and more or less cracked. The particular construction of the heater 10 is not essential, but I have shown it as comprising baffle passages With a fire box and burner 17 located at the upper end of the passage through which the coil extends,the outlet flue 18 being at the bottom or lower end of the heating flue. The arrangement of the coil 16 is such that in its passage therethrough the oil is subjected to an increasing temperature. If desired, more or less of the partially cooled products of combustion may be re-cycl'ed through the bypass 19 into the fire box to moderate the temperature of the freshly formed products of combustion.

From the heating coil 16, the oil vapors are led through a pipe 2O to a system of perforated pipes 21 adjacent the bottom of the shell 1. The pipe 2() is provided with a check valve 22 toprevent the flow of the oil from the shell 1 back to the heating coil 16 in case anything should go wrong. Instead of pumping the light oil directly into the coil 16, it may be preheated in the heat interchanger 7 by the vapors given ofi' from the still. For this purpose, lWe have provided a pipe 23 leading from pipe 15 to one of the chambers of the heat interchanger 7 and a return pipe 24 is also connected to the feed pipe 15. Valves 25, 26 and 27 are providedin these pipes for the control of the flow therethrough. When it is not desired'to preheat the light oil, the-valve 25 is opened and the valves 26, 27 closed, but when the oil is to be preheated valve 25 is closed and valves 26, 27 opened.

The light oil fed from the reservoir 9 is or may be supplemented, after the still is in operation, by reflux condensate from the heat interchangers 5 and 7. For this purpose, branch pipes 28, 29 are connected to the vapor or condensing chambers of the respective heat interchangers and are also connected to a common pipe 30 by which the reflux is connected to a reservoir 31. From the latter the.

reflux condensate may be drawn as required or desired through pipe 32 and valve 33 leading to the inlet side of pump 13. Thus, the reflux condensate may be mixed with the v light oil coming from reservoir 9 or used alone to feed the coil 16.

Preferably, the heavy oil, which may be.

reduced crude, is preheated during the run before being injected into the still 1. For this purpose, the heavy oil reservoir 34 is connected to a. pump 35 by which it is forced through ay meter 36 and line 37 to the liquid space of the reflux condenser or heat-interchanger 5. From the latter, the oil after being preheated flows through pipe 38 into the perforated pipe 39-in the vapor space of the still shell.

The charge of heavy oil with which operation is started is introduced into the shell 1 through the coil 16 in which it is heated, preferably to a temperature approaching its cracking point. A quantity of oil may be thus fed sufcientto half fill the shell. The feed of light oil through the coil 16 is then begun, the ring of the heater 10 being continued. The vapors of the lighter oil from coil 16 are distributed in the lower part of the heavy oil in the still and rapidly heat the latter. When the desired cracking temperature is reached, the feed of additional heavy oil is begun and is continued together with the feed 0f the lighter oil and reflux through the coil 16 during the major portion of the run. The feed of heavy oil is then discontinued, but the feed of light oil continued for a further shorter period, the pressure in the still being slowly -reduced from the pounds normally employed to aboutv 4) pounds to facilitate the vaporization of the heavy oil remaining in the residuum. As the coke in the shell approaches dryness, the feed of light oil through the heater 16 into the shell is discontinued and steam -is introduced in its stead. The feed pipe 15 is provided at 4l) With a steam connection to a suitable source of supply under pressure. For a portion of the time during Which 'steam is introduced, the furnace 10 is fired so that it is superheated to a temperature materially higher than the cracking temperature in the shell 1. The steam is superheated in the coil 16 and being injected into the bottom of the shell l through perforated pipe or pipes 21 thoroughly permeates the coke and heats and assists in carrying off the vapors of the heavy oil remaining in the coke. After the coke is sufficiently freed of liquid hydrocarbons, the fire in the furnace 10 is shut off and the feed of steam continued which cools off the furnace 10 and also the shell 1 and its contents.

lVe will now describe a run on the apparatus disclosed above, exemplifying the practice of our invention:

The shell Was charged with 9050 gallons of reduced crude oil (oil from which the lighter ends had been distilled off) through the coil 16 in which it. Was heated to a temperature somewhat below that at which it would begin to crack. Gas oil was pumped into the heating coil and injected into the body of oil in the shell at a temperature of about 950 degrees F. and in the condition of a vapor. The body of oil Was heated to cracking temperature and 95 pounds pressure was reached in 81/1 hours. Communication to the condenser Was then opened in the usual manner and operation Was continued for 38%n hours While feeding an average of 975 gallons of gas oil per hour. The gas oil in this and the preceding part of the run Was heated to a temperature of about 950 degrees F. in the coil of the heater and vaporized, and the vapor injected through the perforated pipe or pipes 21 into the body of oil in the shell maintained the latter and the infed oil at a cracking temperature between 720 and 750 degrees F. During this on-stream period additional reduced crude was fed to the shell at a rate of about 550 gallons per hour. It was preheated by passing through the liquid space of the reflux tower 5 t-o a temperature of about 590 degrees F. on its Way to the distributing spider 39 in the vapor space of the shell. After the still had been on-stream for 32 hours the feed of reduced crude was terminated and the pressure reduced in the course of two hours from 95 pounds to 40 pounds. During this portion of the run the feed of gas oil from the source 9 and of reflux distillate from the receiver 31 was continued but at a lower rate than that at which distillate was being taken off. The still was run for four. hours at 40 pounds pressure,

feeding gas oil through the heater at 950 de# grees F. during this period to decompose and distill the pitch content of the still charge, this operation being facilitated, as heretofore stated, by the reduction in pressure. At the end of this period the coke in the still was dry as is shown by a rise in temperature from the initial temperature at which pressure reduction Was started (7 50 degrees F.) to a temperature of 830 degrees F. after the still had been on-.stream a total of 381,@ hours.

The oil feed through the heater was then shut off and steam introduced through the heater, (which was still being fired) superheating the steam t0 a temperature of 1000 degrees F. By thus introducing superheated steam into the body of coke and beneath the free surface thereof the temperature of the shell content Was further raised and the partial pressure of the steam promoted the vaporization of the heavier oil remaining in the coke. The introduction of superheated steam Was continued for a period of ,six hours, after which the tire Was shut off but the introduction of steam continued, thus cooling 0E the heater and still. The saturated steam supplied at this time Was passed through the ytower and condenser to a slop tank. Eight hours after Athe fire Was olf the still was opened. The coke bed Was found to be dry and dense but porous in every direction with no pitchy content. lVater was sprayed on the coke to cool it, after which it was readily removed from the shell. During the operation of the still 37260 gallons of gas oil were fed through the heater to the still, and 21150 gallons of reduced crude Were fed to the shell.

98.3 per cent of distillate of the total feed of i heavy oil Was produced. 23250 pounds of coke were obtained from the shellof a quality fully equal to the coke properly made in the conventional direct tired coke still.

The introduction of the vapors of lighter oil and later of steam creates a partial pressure which facilitates vaporization in the shell. Moreover, the introduction of the lighter vapors and the cracking thereof which takes place after coke has been formed deposits carbon in the interstices of the coke bed, thus producing a dense and firm coke but Which is nevertheless readily removed from the shell. By introducing the vapors, Whether of oil or Water or other substance into and throughout the body of coke, they also serve as a carrier assisting in the removal of heavier vapors as they are formed. As all the oil fed to the still, except the residue thereof in the form of coke, appears as distillate the process is an efiicient one both with respect to the percentage of distillate-obllt) tained and the amount of fuel consumed.

The coke is of such high grade that it forms a valuable by-product. Obviously, in place of superheated steam some other gaseous n1aterial or material in the form of vapor may be used.

We claim:

1. A process of cracking heavy hydrocarbons for the production of lighter hydrocar-I bons and coke, Which comprises heating an externally unheated body of the oil to be cracked to a cracking temperature under pressure and distilling off the cracked hydro- 'ture under pressure and distilling o 'bons for the production of lighter hydrocarbons and coke, consisting in heating a body of the oil to be treated toa cracking tem erkat e cracked hydrocarbons formed without the direct' application of heat to said body by inj ecting thereinto vapors of a lighter oil heated to a temperature above the cracking point,

-and thereafter injecting superheated steam into the residuum beneath the free surface thereof while discontinuing the injection of lighter oil vapors.

v3. A process of cracking heavy hydrocarbons for the production of lighter hydrocarbons and coke, consisting in heating a body of oil to`be treated yto a cracking temperature under pressure and distilling olf the cracked hydrocarbons formed without the direct ap- A plication of heat to said body by injecting thereinto vapors' of lighter hydrocarbons heated to a temperature above their cracking point, and thereafter injecting into theresid- Vuum a gas heated to a temperature above the vaporizing point of the liquid components of the residuum while discontinuing the injection of lighter hydrocarbon vapors.

4. .A process of crackin heavy hydrocarbons for the production o lighter hydrocar- Y bons and coke, which consists in maintaining a body of oil to be cracked at a cracking temperature under pressure by injecting thereinto beneath the free surface thereof vapors of hydrocarbons heated above the cracking temperature, thereafter injecting into saidv body a gas heated to a temperature above the vaporizmg point of any hydrocarbons remaining therein while discontinuing the invjection of hydrocarbon vapors, and continuing the injection of said heated gas until the residuum becomes substantially dry coke.

5. YA process of cracking heavy hydrocarbons for the production of lighter hydrocarbons and coke, which comprises maintaining a body of oil to be cracked at a cracking temperature under pressure by injecting into said body beneath the free surface thereof vapors of hydrocarbons at a temperature above the cracking point, feeding additional quantities of heavy oil to said body of oil durin a portion of the period when said vapors o hydrocarbons are being injected thereinto, discontinuing the supply of hea oil and hot hydrocarbon vapors to saidvgody, and further heating the residuum from said body by injecting thereinto beneath the free surface thereof a gasheate'd to a temperature substantiallyabove'the'vaporization point of the heaviest liquid component of said body, and continuing such further heating until the residuum is reduced substantially to dry coke.

'above the cracking point, reducing the pressure on said oil while continuing the feed of vapors, and thereafter injecting a gaseous medium at a temperature above the Vaporizing temperature of the heaviest hydrocarbon remaining in the residue while discontinuing the feed of vapors.

7 A process of cracking heavy hydrocarbons for the production of lighter hydrocarbons and coke, which comprises heating a heavy oil to be cracked to a cracking temperature while maintaining thereon a pressure suiiicient to prevent substantial distillation of uncracked components thereof, injecting into said oil vapors of hydrocarbons at a temperature above thecracking point, gradually lowering the pressure on said oil while continuing the injection of said vapors, and thereafter injecting a gaseous medium heated to a high temperature to drive off any liquid remaining in the residuum while discontinuing the injection of said vapors.

8. A process of cracking heavy hydrocarbons'for the production of lighter hydrocarbo'ns and coke, which comprises heating heavy oil to a cracking temperature under a pres- ,sure suliicient to maintain Athe uncracked oil substantially in liquid condition, injecting into said oil vapors of lighter hydrocarbons at a temperature above the cracking point, lowering the still pressure to about 40 pounds, and thereafter injecting a gaseous medium while discontinuing the injection of hydrocarbon vapors, whereby all liquid components of the residuum are driven off.

9. A process of cracking heavy hydrocarbons for the-production of lighter hydrocarbons and coke, comprising heating a liquid body of the heavy hydrocarbons under pressure, conveying a restricted stream of lighter hydrocarbons through a heating zone and su plying heat to vaporize and crack said llO lig ter hydrocarbons during their passage therethrough, maintaining the said liquid body above the cracking templerature by injecting hot va ors of the lig ter hydrocarbons thereinto below the free surface of said body and driving off the cracked vapors therefrom, subjecting the vapors driven off to a reiuxing operation and returning condensate from the 'said reiiuxing operat1on to the stream of lighter hydrocarbons in the heatingb zone, thereafter injecting into said liquid above the vaporizing point of 'any liquid hyody a vgas heated to a temperature drocarbons remaining therein while discontinuing the injection of hydrocarbon vapors unlil the residuum becomes substantially dry C e. 10. A process of cracking heavy hydrocarbons for the production of lighter hydrocarbons and coke, comprising heating a liquid body of the heavy hydrocarbons under pressure, conveying a restricted stream of lighter 1o hydrocarbons through a heating zone and supplying heat to vaporize and crack said lighter hydrocarbons during their passage f therethrough, maintaining the said liquid body above the cracking temperature by injecting hot vapors of the lighter hydrocarbons thereinto below the free surface of said body, reducing the pressure on said liquid body While continuing the feed of vapors, thereafter injecting into said liquid body a gas heated to a temperature above the vaporizing temperature of the heaviest liquid components While discontinuing the injection of hydrocarbon vapor-s whereby all liq- A uid components of the residuum are 'driven EDWARD W. ISOM. EUGENE C. HERTHEL. HARRY L. PELZER. 

